Physics 401 is offered every fall and summer; Physics 402 is offered every winter and summer. You can take both 401 and 402 in the same summer. These are the algebra-based introductory physics courses.
Physics 407 and Physics 408 are both offered every fall, winter and summer. They are offered concurrently in the summer. These are the calculus based introductory physics courses.
Physics 406 (Astronomy) is offered both semesters and summer.
All higher level required undergraduate courses are offered only once a year and not in the summer. See the undergraduate pages for details on which semester each course is offfered.
Elective courses are offered once every other year.